铝/钛异种合金激光熔钎焊接头界面特性

Interface characteristic and property of Ti/Al dissimilar alloys joint with laser welding-brazing

以铝硅共晶合金为填充材料,采用激光熔钎焊的方法对铝/钛异种合金进行焊接,获得了同时具有熔焊和钎焊双重特征的焊接接头。由于激光局部加热并且有很高的冷却速度,发现在钛合金附近的钎焊界面形成了特殊的形态结构。结果表明,获得的钛合金钎焊区界面金属间化合物厚度很薄,仅在10μm以下。焊缝上部界面金属间化合物较厚,主要呈锯齿状;焊缝下部界面金属间化合物厚度不足1μm,呈薄层状。界面金属间化合物的主要成分为TiAl3,以Ti(SixAl1-x)3结构的置换固溶体形式存在。底部界面容易成为裂纹产生的源头,裂纹多沿界面附近焊缝中的共晶组织扩展,接头的平均抗拉强度为铝母材的85%左右。

With Al-Si eutectic filler wire, Al/Ti dissimilar alloys were joined by the laser welding-brazing process, and the joints with the characters welding and brazing were gained. Due to the local heating of laser and the high cooling rate of the welding seam, special morphology at the interface of titanium substrate and filler metal was found. The results indicate that the maximum of the intermetallic compounds layer is less than 10μm. Moreover, the thickness and structure of the interface layer at different positions of the same joint are various. At the top of the joint, the layer is thick and presents serrated-shape; at the bottom, the thickness of the interface layer is less than 1μm and exhibits lamellar-shape. In addition, TiAl3 is the main phase of the interface layer, which is a typical substitution solid solution of Ti（SixAl1-x）3. Crack starts at the bottom of the joint and grows in the eutectic structure of the seam metal near the brazing interface. The average tensile strength of the joint is up to 85% of that of the Al base metal.